The sensors implemented are infrared sensors, millimetric radars or lidars. The images may be displayed on viewing devices situated on the instrument panel or else on transparent viewing devices displaying the images overlaid on the exterior landscape.
To allow the pilot to locate themself properly, it is sought to detect and to display easily recognizable and identifiable objects. In the subsequent description, these objects are called “elements of interest”. It is understood that these elements of interest must be displayed in the clearest and most intuitive possible manner.
In the case of aeronautical applications, these objects are landing runways in particular. During an instrument-based approach, regulations require the crew to acquire exterior visual references above a certain altitude or at a certain height from the runway so as to be able to continue the landing, otherwise the crew performs a go-around. Starting a few years ago, a specific regulation permits the crew to acquire the visual references by way of a forward-looking sensor of the aircraft rather than by direct vision. It is therefore essential that the presentation of the information arising from the sensors be presented in the best possible manner so as to aid the crew in its decision-making.
A first solution consists in displaying solely the synthetic image in a so-called “SVS” system, the acronym standing for “Synthetic Vision System”, without taking into account the information arising from the image sensors. Thus, in aeronautical use, the system displays solely the terrain and the landing runways on the basis of the position of the aircraft provided by its “GPS” system and its inertial platform. The uncertainty in the position of the aeroplane as well as the precision of the positions of the runways stored in the databases prohibit, however, the use of an SVS in critical phases where the aircraft is close to the ground, such as landing and takeoff.
A second solution consists in displaying solely the image arising from the sensor or sensors. These systems are called “EVS”, the acronym standing for “Enhanced Vision Systems” or “EFVS”, the acronym standing for “Enhanced Flight Vision Systems”. However, the elements of interest are not necessarily easily identifiable. Thus, it is difficult to detect a landing runway with an infrared detector in certain meteorological conditions, such as in foggy weather, for example. The information necessary for landing is then not at the disposal of the crew.
Finally, the existing CVS solutions are based on the simultaneous display of all or part of the synthetic image and of the image arising from the sensor, for example by overlaying the various images and optionally registering the synthetic image on a notable element of the sensor image, or else by inlaying the sensor image in an inset of the synthetic image or else by cropping notable elements of the sensor image and inlaying these elements on the synthetic image. By way of examples, U.S. Pat. No. 7,826,666 entitled “Methods and apparatus for runway segmentation using sensor analysis” and U.S. Pat. No. 7,925,117 entitled “Fusion of sensor data and synthetic data to form an integrated image” describe solutions of this type.
The main defects of these CVS solutions reside in their difficulty of readability and of interpretation by the crew. Another defect is their dependency on the frequency of generation of the images of the sensors which for some sensors, of the radar family for example, may introduce jerkiness into the display of the image. The sensors of infrared type exhibit other drawbacks as already mentioned.
Finally, the “APALS” system, the acronym standing for “Autonomous Precision Approach and Landing System”, proposes a synthetic representation of the landing runway constructed on the basis of navigation data and of detection by a modified weather radar. This system does not make it possible to know whether the runway is actually detected by the radar and does not propose any transition between the synthetic representation of the runway before detection and after detection by the sensor.